1. Field of the Invention
The present invention generally relates to an image forming apparatus of an electrophotographic type or an electrostatic recording type. More particularly, the invention is suitably applicable to an image forming apparatus in which a cartridge, i.e., a process cartridge or a developing unit in the form of a cartridge, can be detachably mounted on the main body of the image forming apparatus, and which has a developer remaining amount detecting member for successively detecting the remaining amount of a developer in a developer container.
Applicable electrophotographic type image forming apparatuses include an electrophotographic copying machine, an electrophotographic printer (such as an LED printer or a laser beam printer), an electrophotographic facsimile machine, and an electrophotographic wordprocessor. The term xe2x80x9ca cartridge detachably attached to the main body of an electrophotographic image forming apparatusxe2x80x9d as used herein means a cartridge formed from at least one of an electrophotographic photosensitive member, charging means which charges an electrophotographic photosensitive member, a developing member which supplies a developer to an electrophotographic photosensitive member, and cleaning means which cleans an electrophotographic photosensitive member, which is then made easily detachable from the main body of the electrophotographic image forming apparatus. In particular, the process cartridge is a cartridge composed of at least one of charging means serving as process means acting on an electrophotographic photosensitive member and the electrophotographic photosensitive member are integrally formed into a cartridge, and is made detachable from the main body of the electrophotographic image forming apparatus.
2. Description of the Related Art
In a conventional image forming apparatus, such as a copying machine or a laser beam printer of the electrophotographic type, an electrostatic latent image is formed by irradiating light (laser beam or the like) in accordance with image information onto an electrophotographic photosensitive member (hereinafter simply referred to as a xe2x80x9cphotosensitive memberxe2x80x9d). The thus formed electrostatic latent image is made visible into a developer image (toner image) by supplying a developer (toner) as a recording material to the latent image by developing means, and an image is formed on a recording medium, such as recording paper from the photosensitive member.
A developer container serving as a developer containing vessel is connected to the developing means, where developer is consumed by forming an image. The developer container, the photosensitive member and the charging means are often formed integrally as a process cartridge detachably mounted on the main body of the image forming apparatus (hereinafter simply referred to as the xe2x80x9capparatus main bodyxe2x80x9d). When the developer is exhausted, for example, the user can form again an image by replacing this process cartridge. This is a developing unit having the developing means and the developer container formed into a cartridge detachably mounted individually on the apparatus main body. In particular, according to the process cartridge process, it is possible to apply the developer, and at the same time, replace other supplies, such as the photosensitive member, by replacing the process cartridge relative to the apparatus main body, thereby permitting a remarkable improvement of maintainability of the apparatus.
For example, for the purpose of knowing from time to time the remaining amount of the developer usable for forming an image in the process cartridge, a process cartridge or an apparatus main body having a developer remaining amount detecting member capable of successively detecting the developer remaining amount level is becoming more popular.
Available means for achieving detection of the developer remaining amount level include a method of measuring the amount of developer through a change in capacitance by means of a capacitor-type bipolar electrode (conductive section), and a method of measuring the amount of developer from a difference between the amount of transmitted light and the amount of received light, produced by emitting light into the developer container.
A detecting method based on a so-called plate antenna, in which a capacitor-type bipolar electrode is arranged, will now be described as an example of the developer remaining amount detecting member. The plate antenna has a pair of electrodes (conductive section) arranged substantially in parallel with each other spaced apart by a prescribed distance. This electrode pair is arranged, for example, in or outside the process cartridge so as to cover the toner in the developer container. That is, this is based on the fact that the capacitance varies with the amount of developer between the electrode pair. This makes it possible to establish a correlation between the amount of developer in the developer container and the capacitance between the electrode pair. It is therefore possible to know at any time the remaining amount level of developer in the developer container by measuring the capacitance by means of the plate antenna. The capacitance of the plate antenna from the current value is generated in one of the electrode pair by impressing an AC bias onto the other.
However, the above-mentioned conventional detecting method of the developer remaining amount level, i.e., the method of measuring the amount of developer from a change in capacitance between two electrode poles may sometimes cause the following problems.
In the conventional method, the capacitance varies with the area of the plate antenna provided in the developer container covered by the developer. A developer remaining amount level is calculated in response to this change, and the result of calculation is notified to the user.
For more recent image forming apparatuses, however, the frequency of use of a laser beam printer is only increasing, and the print volume is also increasing. Furthermore, there is a demand for increasing the printing speed of the apparatus main body (hereinafter referred to as a xe2x80x9cthroughputxe2x80x9d) for improving usability and reducing the output time.
Measures taken so far for increasing the throughput include replacement of the driving motor by one with a higher rotating speed, and reduction of the distance between two recording sheets conveyed when continuously outputting images, known as the paper distance.
Because an increase in the absolute amount of heat results from rotation and fixing along with an increase in throughput, temperature increase and similar problems tend to occur. In order to obtain a high-quality output image, it is necessary to increase the fixing temperature. Particularly, when conveying a small-sized recording medium with a narrow width, such as an envelope and a postcard (hereinafter referred to as the xe2x80x9cpaper feedxe2x80x9d), an abnormal temperature is observed at portions not feeding the paper.
An increasing number of apparatuses have now diversified throughput to cope with higher-accuracy printing (high-resolution image), including provision of a plurality of modes, such as a half-speed mode or high-accuracy printing mode at a very low speed.
The increase in throughput also has an effect on the state of the developer in the developer container. An example is the calculation of the developer in the developer container caused by a stirring unit. When the rotating speed of the driving motor is increased so as to increase the throughput, rotation of the stirring unit provided in the developer container also increases. As a result, the developer in the developer container is actively stirred.
The increase in throughput leads to a considerably reduced acquired data by the developer remaining amount detecting member relative to the image output to a recording sheet. If data are processed for detecting the remaining amount level of the developer with the thus reduced acquired data, the influence of developer circulation in the developer container section caused by stirring by the stirring unit is serious, and the accuracy of detection of the remaining amount level of developer may be deteriorated.
Detection of the developer remaining level has conventionally been conducted, particularly, for the proximity of the developer carrier (in the developer container holding the developer carrier) from the change in capacitance between the developer carrier conveying the developer to the photosensitive member and a conductive plate provided near the pole thereof. In this conventional practice, the capacitance produced between the developer carrier and the plate is measured by use of a developing bias applied/impressed onto the developer carrier.
It is however necessary to measure, not only in the proximity of the developer carrier, but also to measure the developer remaining amount level in the developer container connected to the developing means, because of the increase in the developer loadage of the process cartridge. The amount of developer in the developer container is commonly measured by impressing a bias for detecting the developer remaining amount level onto the plate antenna provided in the developer container in a bias circuit different from the developing bias. In this case, if the bias for detecting the developer remaining amount level is impressed onto the plate antenna simultaneously with the developing bias, it is difficult to accurately detect the developer remaining amount level under the effect of the developing bias. Therefore, the developer amount is measured by impressing the bias for detecting the developer remaining amount level onto the plate antenna immediately before feeding the recording sheets or between recording sheets during continuous paper feeding when the developing bias is not impressed onto the developer carrier. This further reduces the number of acquired data for detecting the developer remaining amount level along with the increase in throughput.
There is also adopted a method of changing the number of revolutions of the driving unit so as to change the throughput. However, a change in the number of revolutions of the driving unit results in large changes in the number of revolutions of the stirring unit, and in circulation of the toner itself in the toner container. In a special mode, in which the number of revolutions of the driving unit is increased for high-resolution output, a problem is encountered in that it becomes impossible to accomplish detection of the toner remaining amount. It is thus difficult to simultaneously satisfy requirements for accurately detecting the developer remaining amount level, on the one hand, and improving throughput with a configuration having a plurality of throughput modes, on the other hand.
In view of the aforementioned problems, the present inventors carried out extensive studies, and obtained the following findings. Even when the throughput is increased, and if the throughput is reduced for the purpose of ensuring a high endurance of the apparatus to prevent temperature increase upon feeding, for example, small-sized recording sheets, or using a low-speed mode provided for high-accuracy printing (to achieve a higher quality of images), it is possible to eliminate the effect of swell resulting from a stirring period of the stirring unit by changing the averaging time of measured data of the amount of developer or the number of data used for averaging in response to the throughput, and to improve the detecting accuracy of the developer remaining amount level by increasing data available from a run of paper feeding process as far as possible.
The present invention was developed to solve the above-mentioned problems, and has an object to provide an image forming apparatus, having a plurality of printing speeds (throughput), which permits successive detection of the remaining amount of developer at a high accuracy in response to the printing speed (throughput).
The present invention provides an image forming apparatus capable of forming an image at any of a plurality of printing speeds, comprising: a developer container containing a developer, a developer amount detecting member which detects a developer remaining amount in the developer container and outputs the detection value; and a control section which detects a developer remaining amount by subjecting a plurality of detection values from the developer amount detecting member to an arithmetic processing to detect the remaining amount of developer; wherein the control section changes the arithmetic processing in response to the printing speed.
The present invention also provides an image forming apparatus capable of forming an image at any of a plurality of printing speeds, comprising: a developer container containing a developer; a developer amount detecting member which detects a developer remaining amount in the developer container and outputs the detection value; a conveying section for conveying a recording medium on which an image is to be formed; and a control section which detects a remaining amount of developer by arithmetically processing a detection value output from the developer amount detecting member for each run of conveyance of the recording medium to the conveying section; wherein the control section changes the detecting period of the detection value from the developer amount detecting member for each run of conveyance of the recording medium to the conveying section, in response to the printing speed.
The present invention provides a controlling method of an image forming apparatus capable of forming an image at any of a plurality of printing speeds, where the image forming apparatus comprises: a developer container containing a developer; a developer amount detecting member which detects a developer remaining amount in the developer container and outputs the detection value; and a control section which detects a developer remaining amount by subjecting a plurality of detection values from the developer amount detecting member to an arithmetic processing to detect the remaining amount of developer; the controlling method comprises: a first step of detecting the kind of a recording medium for forming an image; a second step of determining a printing speed in response to the kind of the recording medium detected in the first step; and a third step of detecting the remaining amount of developer by changing the arithmetic processing in response to the printing speed determined in the second step.
The present invention provides another controlling method of an image forming apparatus capable of forming an image at any of a plurality of printing speeds, where the image forming apparatus comprises: a developer container containing a developer; a developer amount detecting member which detects a developer remaining amount in the developer container and outputs the detection value; a conveying section for conveying a recording medium on which an image is to be formed; and a control section which detects a remaining amount of developer by arithmetically processing a detection value output from the developer amount detecting member for each conveyance of a recording medium to the conveying section, the controlling method comprises: a first step of determining a printing speed in response to the image forming mode of the image forming apparatus; a second step of changing the detection period of a detection value from the developer amount detecting member for every conveyance of a recording medium to the conveyance section in response to the image forming mode determined in the first step; and a third step of detecting a remaining amount of developer using a detection value detected in the second step.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings).